FIGURE 4.7-2 (a) The circuit considered in Example 4.7-2. (b) The circuit after replacing the voltmeter by an open circuit,
(c) The circuit after labeling the meshes.
Solution
Figure 4 7-26 shows the circuit after replacing the voltmeter by an equivalent open circuit and labeling the voltage
measured by the voltmeter. Figure 4.7-2c shows the circuit after numbering the meshes. Let i1 and i2 denote the
mesh currents in meshes 1 and 2, respectively.
The voltage across the dependent source is represented in two ways. It is Aia with the + of reference
direction at the bottom and —7.2 V with the 4- at the top. Consequently,
Aia = —(—7.2) = 7.2 V
The controlling current of the dependent source, za, is the current in a short circuit. This short circuit is common to
meshes 1 and 2. The short-circuit current can be expressed in terms of the mesh currents as
ia=i1-i2
Apply KVL to mesh 1 to get
10i1-36=0 => i1=3.6A
Apply KVL to mesh 2 to get
4i2 + (-7.2) = 0 => i2 =1.8A
finally A=Aia/ia =Aia/i1-i2 =7.2/3.6-1.8 = 4V/A